This commit loses some indexes, unique constraints etc. that were
manually added by the old migrations. I plan to add them to a new
migration in a subsequent commit.
(imported from commit 4bcbf06080a7ad94788ac368385eac34b54623ce)
This needs to be deployed to both staging and prod at the same
off-peak time (and the schema migration run).
At the time it is deployed, we need to make a few changes directly in
the database:
(1) UPDATE django_content_type set app_label='zerver' where app_label='zephyr';
(2) UPDATE south_migrationhistory set app_name='zerver' where app_name='zephyr';
(imported from commit eb3fd719571740189514ef0b884738cb30df1320)
